Answer:
A: When a planet is closer to the Sun, its speed is greater than when it is farther away.
Explanation:
Kepler's laws establish that:
- All the planets revolve around the Sun in an elipse orbit, with the sun in one of the focus (Kepler's first law).
- A planet describes equal areas in equal times (Kepler's second law).
- The square of the period of a planet will be proportional to the cube of the semi-major axis of its orbit (Kepler's third law).
Where T is the period of revolution and a is the semi-major axis.
Since planets orbit around the Sun in an ellipse, with the Sun in one of the focus, in some moments of their orbit they will be closer to the Sun (known as perihelion). According with Kepler's second law to complete the same area in the same time, they has to speed up at their perihelion and slow down at their aphelion (point farther from the sun in their orbit).
That increase in the orbital velocity as a consequence of the distance can be prove by the Universal law of gravitation:
(1)
Where G is the gravitational constant, M and m are the masses of the two objects and r is the distance between them.
(2)
Where m is the mass and a is the acceleration. Equation (2) can be replaced in equation (1).
(3)
Since it is a circular motion, the centripetal acceleration is defined as:
(4)
Replacing (4) in (3) it is got:
(5)
Notice that m in equation (5) represents the mass of the planet while M is the mass of the Sun.
Equation (5) can be expressed in term of v:
(6)
Hence, if the distance increases the orbital velocity decreases (inversely proportional).
work done is product of force and displacement of point of application of force
so here we have to check the product of force and displacement both
Now we will put the least to maximum work in the following order
1. -A man exerts strenuous effort in pushing a stationary wall
2. -A flea pushes a speck of dirt 1 cm
3. -A farmer pushes a 2 kg wheelbarrow 20 m
4. -A cannon launches a 3 kg cannonball a distance of 200
5. -A 2000 kg car travels 400 m down a road
6. -Space shuttle Atlantis launches from the ground into near-Earth orbit
Answer:
mirrors set parallel to each other at 45 degree angle.
real
<h2>Answer: The image is formed at infinity and its nature is virtual</h2>
A converging lens is a type of optical lens that is<u> thicker at the center than at its edges</u>; this type of lens concentrate or converge (that is why its name) at a point the rays of light that pass through it.
If we talk about the formation of the image, its location and nature will depend on where the object is located with respect to the focal length of the lens. So, in general:
- If the object is considerable away from the focal point, a real image (which can be projected on a screen) will be formed, inverted and smaller than the object.
-If the object is very close to the focal point, a virtual image will be observed (it is given this name because the image can not be projected on a screen) upright and bigger than the object.
<h2>Now, if the object is placed right at the focal point, the image would be <u>formed at infinity </u>(<em><u>therefore, we would not see it</u></em>) and its <u>nature</u> would be <u>virtual.</u></h2><h2><u /></h2>
According to this, the image of the coin will not be seen.
The cross section is the little tiny circle you see when you cut a wire
and look at the flat, cut end.
The cross-sectional area of the wire is the area of that little circle.
It's equal to
Area = (pi) x (1/4) x (Diameter of the wire)²
